366 



ANATOMY OF VERTEBRATES. 



di-plenr-apopliyses, ib. d, are long and incline forward and down- 

 Avard. Long hypapophyses, ib. h, are also developed. 



The thoracic ribs consist of bony pleur- and gristly h^m- 

 apophyses : of these the seven anterior pairs, as a rule, directly 

 join the sternum, which then consists of six bones or ' stern ebers.' 

 In the Beaver, Porcupine, Coypu, and a few others, there are 

 eight pairs of ' true ribs : ' in an Acuchy with this number I 

 found nine sternal bones, the foremost representing an ' epi- 

 sternal' articulated to the '^manubrium.' 

 The first rib is the shortest, unusually so in 

 Hydromys, and has often a partial articu- 

 lation with the last cervical vertebra. The 

 neural spine of the second dorsal is com- 

 monly the longest. 



232 



In the Beaver, fig. 230, the 

 sacrum consists of four anchy- 

 losed vertebrae : the articular sur- 

 face for the ilium is almost con- 

 fined to the transverse process of 

 the first of these vertebrae : those 

 of the last are the longest. The 

 sacral nerves directly perforate 

 the neurapophyses of the last two vertebras, anterior to the vacuity 

 left between the bases of the transverse processes. The neural 

 arches of the first six caudal vertebrae are similarly perforated. Their 

 transverse processes are long, horizontally flattened, and terminally 

 expanded ; and the vertebrae, after these processes subside, are 

 remarkable for their large size, and a certain degree of corre- 

 spondence of shape mth the broad, flat, scaly tegumentary tail 



Jerljoa iDipus Sagitta). 



